“Like many courtships, this one was sealed with a ring. The Italian conductor Gianandrea Noseda, the music director of the National Symphony Orchestra in Washington, had left an operatic post this spring at the Teatro Regio in Turin, Italy, amid administrative and political upheaval. The Zurich Opera House came calling. ‘I said, ‘Do you want to be my chief conductor?” Andreas Homoki, the artistic director in Zurich, recalled recently. Then he offered Mr. Noseda the icing on the cake: ‘I said, ‘Do you wanted to do the Ring with me?””